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Fresh off the block from Computex, Microsoft’s engineers at the Building Windows 8 blog have unleashed another blog post. The new details concern Windows 8’s audio/visual playback engines, format support, and feature sets. As Windows 8 MC Steven Sinofsky notes, video playback has changed considerably in the past few years, and Windows 8 is designed to support the shifting models.

When running on a Windows Certified PC, Windows 8’s video decoding for “common media tasks” will be offloaded to a dedicated hardware subsystem. The company claims that this will dramatically lower power consumption and improve battery life, and has a graph to prove it. The image below shows the purported improvement in CPU usage between Windows 7 and Windows 8 while playing back a 720p VC1/H.264 clip in WMP, HTML5, and a webcam capture preview.

Microsoft’s BW8 blog is normally quite good about creating clear, easy-to-parse graphs, but this one is an exception. It’s not clear whether Microsoft is comparing Windows 7 performance with CPU-only decode against W8-compatible hardware, or if the W7 system is already taking advantage of hardware acceleration.

The difference isn’t trivial. AMD, Nvidia, and Intel have all shipped integrated GPUs with hardware-assisted video decode for a number of years. It’s not even clear what CPU was used, though we’re guessing it was something from Intel’s Atom family based on the high CPU utilization. CPU utilization isn’t the best metric in any case — Windows considers a single-core CPU w/ Hyper-Threading to be two full cores when reporting CPU percentages.

There are additional improvements elsewhere in the stack. The audio engine will now buffer a much higher amount of content when in steady playback mode, which allows the chip to sleep for more than a second at a time, as opposed to a 10ms sleep cycle. That might not seem like much, but in computational terms, it’s huge. According to Microsoft, these changes allow the CPU to spend up to 100x more time asleep while handling audio, which should translate into significantly improved battery life.

Improving battery life with better buffering technology, however, is only one aspect of the team’s work. An equal amount of under-the-hood optimization has been done to ensure low-latency communications are possible when using voice-over-IP (VoIP) services, or chatting via webcam.

Microsoft’s goal for Windows 8 was to reduce what it calls “glass-to-glass” latency to below the 100ms audio/145ms video latencies set by the TIA 920 standard. The Windows 8 media pipeline can move from the high-latency, power-saving mode it uses for steady audio playback to the low-latency communication mode for VoIP services and back without the end user taking any additional action at all. The process is designed to be invisible and handled entirely in the background.

Formats, video metadata, and copy protection

There aren’t many surprises in Microsoft’s list of available and preferred formats, but it’s disappointing to see that native .MKV (Matroska Multimedia Container) support didn’t make the cut. The post notes that developers are free to package codecs for standards like FLAC, MKV, and Ogg alongside the apps that use them. Codec installation would be handled simultaneously with app installation, rather than requiring a separate download like the popular K-Lite codec packs.

The gaps between Windows RT (aka Windows on ARM) and the x86 flavor are fairly limited. Microsoft’s “hardware dependent” label is a bit misleading, given that all major GPUs from Intel, AMD, and Nvidia have offered hardware-accelerated support for H.264, VC-1, Flash, and DXVA for a number of years.

Windows 8 will also be able to parse video metadata regarding field orientation in MP4 and VC-1/WMV video and will automatically rotate both thumbnail content and full video. The new OS also supports adaptive bitrates, which facilitate streaming by kicking off at low bitrates and scaling up to higher levels once content has been buffered.

Finally, there’s copy protection. Microsoft calls its new solution “PlayReady,” and it’s compatible with both streaming services and content downloading. The company doesn’t say how PlayReady interfaces with Intel’s hardware DRM scheme, Intel Insider, or whether it’s designed to interface with the UltraViolet standard. The post states that “the Media Foundation extensibility model allows for third parties to integrate their custom content protection systems with built-in hardware-accelerated video decoding. If a service needs to use a custom streaming format or content protection system, it can integrate its own technology without having to compromise on decoding quality or battery runtime.”

Other options include expanded “Play To” functionality, which allows you to instruct content on Device A to play on Device B, auto-pausing audio streams that resume when the overriding video/audio finishes, and wide support for 3D viewing, DSP functions, and subtitle display.

The wide range of changes takes some of the sting out of MS’ decision to remove DVD playback from Windows 8; the company has clearly made content playback and control a central feature of the new operating system.

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